Fuel used in internal combustion engines is typically contained in a tank or reservoir as a mixture. Depending on the source of the fuel, it may comprise one or more different fuel components in an unknown ratio. Automobile fuel, for example may be gasoline, including any of its variant blends of aliphatic, olefinic, and/or aromatic hydrocarbons. It may further include various alcohols such as methanol, ethanol, propanol, butanol, pentanol, octanol, and the like. Other components that may be present include octane improvers such as methyl tertiary butyl ether (MTBE) and the like.
Each of these fuel components requires different parameters for optimal combustion. These parameters include specific air to fuel ratios, spark plug timing, injector volume, and the like. When the precise composition of the fuel is unknown, or is ever-changing, accurate determination of the optimal combustion parameters depends on being able to quickly and accurately sense fuel mixture composition and other parameters indicative of optimal end use parameters. One approach to optimal engine operation requires the ability to sense characteristics of the fuel, and adjust the operational conditions of the engine accordingly.
Systems have been designed to sense the characteristics of various blends of fuels, such as gasoline and methanol. U.S. Pat. No. 4,438,749 to Schwippert is directed to an optical sensor that uses the overall refractive index of the fuel as an indication of composition. Aromatic content of the fuel and clouding of the optical sensor elements over time can result in variations of refractive index that lead to inaccuracy in the sensor output.
Microwave fuel composition sensors utilize the fuels overall dielectric constant through microwave attenuation. Besides adding significant cost, these sensors operate at extremely high frequencies (e.g., 1-30 Giga Hertz) and generate amounts of electromagnetic noise that can interfere with other electronic components.
Sensors, which utilize the fuel mixture as a dielectric in a capacitive cell, are also capable of correlating the dielectric constant of a fuel mixture to its composition. These sensors have the benefit of being rugged and can be designed for used in environments in which other sensors would be unacceptable. Unfortunately, the conductivity of various fuel mixtures varies in a non-linear relationship depending on component concentrations. This phenomena is made worse by impurities, especially water. These sensors also need to be made relatively large as compared to other sensors to achieve the level of sensitivity required to sense fuel in an efficient manner. Space and size limitations imposed by design, and the need to minimize void volume in fuel delivery systems, among other factors, have limited the usefulness of capacitive fuel sensors in automotive fuel delivery system applications. A rugged, compact sensor having a sensitivity capable of discriminating between a wide range of fuel blends would be beneficial to optimal combustion of fuel, especially in an internal combustion engine.
Described herein is a sensing element for measuring a fluid composition comprising: an electrode base having a first electrode and a second electrode disposed thereon; the first electrode and said second electrode being electrically isolated from one another; said first electrode and said second electrode being configured, dimensioned, and positioned to define a gap therebetween such that electrical conduction through the fluid within said gap is proportional to the composition of said fluid.
Also disclosed is a method of sensing a fluid composition comprising: contacting said fluid composition with a sensing element in communication with a circuitry, said sensing element comprising: an electrode base having a first electrode and a second electrode disposed thereon; said first electrode and said second electrode being electrically isolated from one another, except through said circuitry; said first electrode and said second electrode being configured, dimensioned, and positioned to define a gap therebetween such that electrical conduction through a fluid within said gap is proportional to the composition of said fluid; a first electrical connector to provide electrical communication between said first electrode and said circuitry; and a second electrical connector to provide electrical communication between said second electrode and said circuitry; determining said electrical conduction of said fluid; and correlating said electrical conduction to said fluid composition.
Further disclosed herein is a combined fluid pressure regulator and assembly for sensing a fluid composition, comprising: a sensing element disposed within a fluid flow path located within a fluid pressure regulator housing; said sensing element comprising: an electrode base having a first electrode and a second electrode disposed thereon; said first electrode and said second electrode being electrically isolated from one another except through an external circuitry; said electrode base having an inner surface and an outer surface separated by a thickness; said outer surface being continuously disposed around a central axis to form an essentially cylindrical shape; said electrode base defining a flow path parallel to said central axis having a flow path length; said first electrode being a plurality of first electrode teeth disposed on said inner surface depending away from said outer surface towards said central axis; said second electrode being a plurality of second electrode teeth on said inner surface depending away from said outer surface towards said central axis; said first electrode teeth and said second electrode teeth being configured, dimensioned, and positioned in a substantially alternating pattern to define a plurality of gaps therebetween such that electrical conduction through a fluid within said plurality of gaps is proportional to a composition of said fluid; said fluid pressure regulator housing comprising a first fluid conduit and a second fluid conduit which allows said fluid to travel through said fluid flow path located with said fluid pressure regulator housing; a regulator valve mounted therein responsive to a fluid demand and disposed in sealing communication between said first conduit and a bypass conduit; a first electrical connector being channeled through a sealing member disposed in said regulator valve to provide electrical communication between said first electrode and said external circuitry; and a second electrical connector being channeled through a sealing member disposed in said regulator valve to provide electrical communication between said second electrode and said external circuitry.
The above described and other features are exemplified by the following figures and detailed description.